Oilpan: fix WebSockets unit test GC plugin failure.

Oilpan: fix WebSockets unit test GC plugin failure.

The MockWebSocketChannelClient's trace() method must delegate to the
mixin's trace() method (even if it is empty.)

R=haraken@chromium.org
BUG=
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178826

[sof, 2014-07-24 08:22:52]

Please take a look.

(I haven't worked out where this started failing.)

[haraken, 2014-07-24 08:24:50]

LGTM

[sof, 2014-07-24 08:36:55]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2014-07-24 08:38:00]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sigbjornf@opera.com/418803003/1

[sof, 2014-07-24 08:38:52]

On 2014/07/24 08:24:50, haraken wrote:
> LGTM

Thanks, sending this along, but there's a large amount of unit test failures
(leaks) with ToT.

[commit-bot: I haz the power, 2014-07-24 08:42:45]

Change committed as 178826

[sof, 2014-07-24 09:08:40]

On 2014/07/24 08:38:52, sof wrote:
> On 2014/07/24 08:24:50, haraken wrote:
> > LGTM
> 
> Thanks, sending this along, but there's a large amount of unit test failures
> (leaks) with ToT.

Trying to address that in https://codereview.chromium.org/412173002/